Covers and window materials for industrial devices such as semiconductor production devices, flat panel display production devices and the like; covers and window materials for industrial machines such as cranes, excavators and the like; window materials for automobiles, vehicles, seacrafts and aircrafts; and window materials for dwellings, hospitals and office buildings are conventionally formed glass. Recently, synthetic resin materials are widely used for the economic points of view of weight, fuel efficiency, and the like. Especially, polycarbonate resin laminates having superb impact resistance, heat resistance, and transparency are preferable. However, the above-listed products are used outdoors and so exposed to wind and rain or sunlight, or used under the conditions of high temperature and high humidity inside vehicles. Therefore, the polycarbonate resin laminates have problems of being clouded or peeled off due to the deterioration of the adhesive layer thereof. The above-listed products are often required to have a certain level of bendability from the viewpoints of design and safety. The polycarbonate resin laminates need to be bent at high temperature because of the high heat resistance thereof, and therefore, have problems of being warped, air-bubbled, whitened, peeled off or the like.
As an adhesive for a polycarbonate resin laminate, Patent Document 1 describes visible light-curable adhesives. A usual visible light-curable adhesive does not have a sufficient adhesive force, and so there are problems that the polycarbonate resin laminate is peeled off when being bent at high temperature, and also is air-bubbled or whitened due to the deterioration or decomposition of the adhesive layer. Under the conditions of high temperature and high humidity of outdoors or inside of a vehicle, there are problems that the polycarbonate resin laminate is clouded or peeled off. For example, the visible-light curable adhesive described in the examples of Patent Document 1 (BENEFIX PC produced by Adell Corporation) was clouded under the conditions of high temperature and high humidity (65° C.-95% RH-24 h).
As an adhesive for a polycarbonate resin laminate, Patent Document 2 describes moisture-curable hotmelt-type adhesives, thermoplastic polyester resin adhesives, and thermoplastic silane-denatured resin adhesives. However, all of these adhesives do not have a sufficient adhesive force when being heated at a temperature of 130° or higher and so have problems that the polycarbonate resin laminate is peeled off when being bent at high temperature and also is air-bubbled or whitened due to the deterioration or decomposition of the adhesive layer. Under the conditions of high temperature and high humidity of outdoors or inside of a vehicle, there are problems that the polycarbonate resin laminate is clouded or peeled off.
As an adhesive for a polycarbonate resin laminate and an acrylic-based resin laminate, Patent Document 3 describes polyurethane-based adhesive films. With such a polyurethane-based adhesive film, although a certain level of adhesive force is obtained, the polycarbonate resin laminate or the acrylic-based resin laminate is whitened at a bent portion and the visibility is significantly decreased. Under the conditions of high temperature and high humidity of outdoors or inside of a vehicle, there are problems that the polycarbonate resin laminate or the acrylic-based resin laminate is clouded or peeled off.
Meanwhile, recently, there is a serious problem that an electromagnetic wave generated from electronic devices such as personal computers, mobile phones, flat panel displays represented by liquid crystal displays and plasma displays, touch panels, car navigation systems, mobile information terminals and the like, motors of industrial machines, and the like causes malfunctions of the industrial machines and the electronic devices or communication failures. Moreover, the electromagnetic wave is indicated as possibly having an adverse influence on human bodies. In order to prevent the so-called electromagnetic interference (hereinafter, referred to as the “EMI”), measures are now taken using various electromagnetic wave shield materials.
Since a single electromagnetic wave shield material does not provide a sufficient strength, electromagnetic wave shield materials are laminated using any of various optically transparent resin substrates or glass substrates. From the viewpoint of safety, an optically transparent electromagnetic wave shield laminate using, as a substrate, a polycarbonate resin having superb impact resistance and heat resistance is preferable. When being used for covers or housings of industrial devices such as semiconductor production devices and the like, industrial machines, various electronic devices and the like, or for window materials or covers of automobiles, vehicles, seacrafts, aircrafts, dwellings, hospitals, office buildings and the like, the optically transparent electromagnetic wave shield laminate is often required to have a certain level of bendability from the viewpoints of design and safety. A polycarbonate resin needs to be bent at high temperature because of the high heat resistance thereof, and therefore, there are problems that an optically transparent electromagnetic wave shield laminate formed of a polycarbonate resin is warped, air-bubbled, whitened, peeled off or the like. Therefore, no technology for bending the optically transparent electromagnetic wave shield laminate has been disclosed.
As an adhesive for an optically transparent electromagnetic wave shield laminate, Patent Documents 4 and 5 describe acrylic-based, rubber-based, silicone-based, polyurethane-based, and polyester-based transparent tacky agents. Since a tacky agent does not have a sufficient adhesive force, there are problems that the optically transparent electromagnetic wave shield laminate is peeled off when being bent at high temperature and also air-bubbled or whitened due to the deterioration or decomposition of the adhesive layer.
As an adhesive for an optically transparent electromagnetic wave shield laminate, Patent Documents 6 and 7 describe adhesive compositions containing, as a main component, ethylene-vinyl acetate (EVA) copolymer adhesive composition or a copolymer of ethylene, vinyl acetate and/or (meth)acrylate-based monomer. All of these materials cause faults of being air-bubbled, whitened or peeled off when being bent at high temperature due to the deterioration or decomposition of the adhesive layer.
As an adhesive for an optically transparent electromagnetic wave shield laminate, Patent Document 8 describes hotmelt-type adhesives of an ethylene-vinyl acetate (EVA) copolymer or an ethylene-acrylic acid ester copolymer. All of these materials have problems of being air-bubbled, whitened or peeled off when being bent at high temperature due to the deterioration or decomposition of the adhesive layer.
As an adhesive for an optically transparent electromagnetic wave shield laminate, Patent Document 9 describes urethane-based adhesives. With such a polyurethane-based adhesive, although a certain level of adhesive force is obtained, the optically transparent electromagnetic wave shield laminate is whitened at a bent portion and the visibility is significantly decreased. This document discloses no explanation or example regarding the detailed compositions of the adhesives or processability thereof.
Patent Document 1: Japanese Laid-Open Patent Publication No. H08-39746
Patent Document 2: Japanese Patent No. 3994404
Patent Document 3: Japanese Laid-Open Patent Publication No. H09-239936
Patent Document 4: Japanese Laid-Open Patent Publication No. 2006-319251
Patent Document 5: Japanese Laid-Open Patent Publication No. H10-163673
Patent Document 6: Japanese Laid-Open Patent Publication No. 2001-26758
Patent Document 7: Japanese Laid-Open Patent Publication No. 2001-19925
Patent Document 8: Japanese Laid-Open Patent Publication No. 2004-140283
Patent Document 9: Japanese Laid-Open Patent Publication No. H11-330778